Bumi, the Indonesian coal miner that has been at the centre of a storm over corporate governance, took a significant step towards improving its reputation yesterday when the chairman, Samin Tan, and co-chairman, Indra Bakrie, waived their joint 29.9 per cent voting block at the company's annual general meeting.

But the impact of the move – intended to sidestep criticism that the company's top executives are wielding too much shareholder influence – was undermined immediately by the fact that the co-chairman did not turn up to the meeting. Mr Bakrie, who was Bumi's chairman until a board shake-up in March, was called away on urgent business in the Far East a few days ago, a company spokesman explained.

Speaking at the AGM, Andrew Hickman, a shareholder and campaigner for anti-corruption group Down to Earth, said: "I find it quite surprising and disappointing that Mr Bakrie isn't here," adding that he'd wanted to address most of his questions to the co-chairman.

Tom Powdrill, of the shareholder advisory group Pirc, added: "It's fairly standard to expect board members to attend AGMs as it is the principal point at which formal contact is made with shareholders.

"It may not be a red-card offence, but if you're a director of a company it is your business to attend – especially if you hold a large stake in that company," he added.

Nat Rothschild, the financier who created Bumi a year ago by reversing two Jakarta-based coal miners into a London-listed cash shell, was keeping a low profile at the meeting in Mayfair yesterday.

Mr Rothschild, a non-executive director of Bumi with a substantial minority shareholding, was ousted from the co-chairman's seat in March after falling out with the Bakrie brothers and Mr Tan. The dispute erupted after a letter Mr Rothschild sent to then chief executive Ari Hudya criticising corporate governance at the company was leaked to the press.

After greeting members of the audience with a handshake on entering the room, Mr Rothschild sat on the edge of the scene and was silent throughout the meeting.

Answering accusations that Bumi was conducting the AGM in an non-transparent manner, Mr Tan said: "Transparency – that's exactly what we're here for. I know there have been some problems in the past…but things cannot be changed overnight, they take some time."

However, four shareholders separately accused the Bumi board of failing to engage with their concerns in a grumpy meeting. At one point, Sir Julian Horn-Smith, the former Vodafone chief executive who is Bumi's senior independent director, said of one shareholder claim: "Frankly speaking, this is the first we've heard of it."

He added that he would be perfectly happy to discuss specific points of substance with shareholders, except that he hadn't heard any made. The shareholders, whose grievances included concerns about the environment and Bumi's treatment of its workers, were unimpressed.

"It's sounds to me as if you don't care," said Roger Moody, one of the shareholders.

A spokesman for Bumi said: "It's unfortunate that these shareholders made no attempt to engage with us [before the meeting]. We would be very happy to engage, it would achieve a lot more. If there are detailed allegations, come and talk to us, we are not hiding behind anything."